Patent GB-805640-A (GB)
Title: Improvements in or relating to two-stroke internal combustion engines
IPC: F02D15/00
Filed: 1956-03-20
Abstract: 805,640. Two-stroke engines; starting fuel-injection engines. NORDBERG MANUFACTURING CO. March 20, 1956 [March 23, 1955; March 24, 1955; March 6, 1956], No. 8683/56. Classes 7(2), 7(3), and 7(6) [Also in Group XXIX] In a two - stroke engine having an exhaust - driven supercharger 22, Fig. 1, delivering through an intercooler 30, part of the charge in the cylinder 10 is rejected on each cycle and passed back to the air intake pipe 32. In Fig. 1, the rejected charge, controlled by an auxiliary camactuated valve 42, passes through a passage 44 and auxiliary intercooler 46 to the intake manifold 14. The time of opening of the valve 42 is varied in accordance with load by a spring-loaded piston 62 actuated by the intake manifold pressure tapped off from pipe 44 through a pipe 66, the piston 62 moving a camfollower 56 to advance the closing point of the valve 42, thereby reducing the amount of air rejected, as the load decreases. The pipe 44 may be connected tc the intake pipe 32 upstream of the interoooler 30, the auxiliary cooler 46 being then omitted. In a modification, Fig. 3, the valve 42 is replaced by auxiliary piston oontrolled ports 84 situated above the exhaust ports 86 and opening into a chamber 82 connected through a valve 87 to the intake manifold 14. The timing of valve 87 is varied according to load by a piston 98 actuated by intake manifold pressure and connected to two idler sprockets 104, 106, in the chain drive 96 of camshaft 88. In a modification, the charge from the exhaust turbo - supercharger is further compressed in an engine driven supercharger and in a further modification the fuel injector 38, Fig. 1, is ,supplied at starting by an injection pump supplying starting fuel and at normal running by a separate pump supplying normal fuel, both pumps being controlled by a governor and brought into action in succession. A heating coil may alternatively be provided to facilitate starting -and the rejected charge may be filtered. In an opposed piston engine, Fig. 11, supplied with air through an intercooler 232 by an exhaust driven supercharger 228, the rejected charge is controlled by a valve 246 actuated by a cam 252 through a cam-follower lever 258 pivoted on an eccentric 288 which is adjusted by a rack 284 actuated in accordance with engine load by a fluid pressure servomotor 280 controlled by a piston device 264 actuated by intake manifold pressure. In a modification, Fig. 14, the auxiliary rejection valve 246 is omitted and rejection of charge takes place through the intake ports, the amount of rejection being varied in accordance with load by adjustment of the driving gear interconnecting the upper and lower crankshafts 312, 314. At no load the pistons are in phase and no rejection occurs but as the load increases an intakemanifold-pressure-operated piston 344 and servo-mechanism 338 swings a gear wheel 322 about a pivot 332 and advances the timing of the lower piston relative to the upper piston whereby the exhaust ports controlled by the upper piston close before the intake ports controlled by the lower piston and rejection of charge occurs. In an engine having, in addition to the exhaust driven supercharger, an enginedriven compressor 98a, Fig. 20, ignition at starting and low loads is facilitated by bypassing some of the supercharging air from the intake manifold 22a to the exhaust manifold 26a through a passage 94a under the control of a governor-controlled throttle valve 96a. Alternatively, the supply of supercharging air is reduced at low loads by control of the air entering the supercharger.